Hexavalent chromium [Cr(VI)] is widely used in various industrial processes and has been recognized as a carcinogen. As the first line of host defense system, the immune system can be a primary target of Cr(VI). T cell population represents a major arm of the immune system that plays a critical role in host anti-tumor immunity. Dysfunction of T cells, such as exhaustion under the persistent presence of tumor antigen, compromise host anti-tumor immunity resulting in oncogenesis. Previous studies have shown Cr(VI) exposure alters the phenotype of human peripheral blood lymphocytes. However, the mechanism of the alteration and whether such an alteration in immunity affects immunosurveillance and promotes carcinogenicity are not clear. Using a culture of mouse splenic T cells as an in vitro model system, the present study assessed the effects of Cr(VI) on T cells, as the first step in our investigation of the mechanism underlying Cr(VI)-inhibited immunosurveillance and carcinogenesis. Our results showed that Cr(VI) decreased the viability of CD4+ and CD8+ T cells and inhibited their activation, proliferation, cytokine release and cytolytic function.